1. Field of the Invention
The present invention relates generally to a, so-called, hybrid transmission for a hybrid vehicle in which a plurality of power sources such as an engine and a motor are mounted. Specifically, the present invention relates to the hybrid transmission which is capable of performing a continuously variable transmission by means of a differential unit such as a planetary gear mechanism.
2. Description of the Related Art
A Japanese Patent Application First Publication No. Heisei 11-301291 published on Nov. 2, 1999 exemplifies a previously proposed hybrid transmission. In the previously proposed hybrid transmission, two simple planetary gear groups are equipped coaxially. An engine revolution is distributed and inputted to ring gears of these planetary gear groups and, on the other hand, an output end to a vehicular road wheel drive system is coupled to carriers of both of the planetary gear groups. Two separate motor/generators are coupled to sun gears of both of the planetary gear groups. In addition, a brake enabled to fix both ring gears with the engine revolution zeroed is installed within the previously proposed hybrid transmission.